1. Field of the Invention
This invention relates to a method and apparatus for transporting an oil rig, and more particularly to a system and method for partially disassembling an oil rig or other large structure to provide easier transport.
2. Background Art
Oil rigs are huge structures that need to be moved from time to time to accommodate drilling and/or pumping from new oil reserves. Oil rigs are common in many parts of the world, including the Middle East, Siberia, and Alaska. Although the structure of an oil rig may vary somewhat depending on the terrain in which the rig is placed or over which it travels, the general rig structure and function remain the same.
Typically, and especially on the North Slope of Alaska, each oil rig includes a rig substructure upon which a rig floor and mast are positioned. The rig substructure is often self-motile, permitting it to be driven from one drilling site to another. With respect to such oil rigs, a rig floor and mast are typically attached to the top of the rig substructure. Thus, the entire oil rig may be transported, as necessary, under its own power.
Generally, oil rigs are massive structures. A typical oil rig weighs over two million pounds and is approximately 100 feet tall. Thus, the travel speed of a self-powered rig is rather limited, and adverse terrain may considerably slow the rig (if not prevent travel completely). For example, it is extremely difficult to transport a self-motile across tundra, due to the uneven surface and snow, as well as the challenges posed by rivers, crevasses, or other discontinuities in the tundra surface.
On the North Slope, an ice-road is typically built to move oil rigs over tundra in order avoid building a permanent road, which may create a relatively heavy environmental impact. Unfortunately, ice roads are comparatively expensive to build, and take a great deal of time to complete. In addition, when moving an entire rig by driving the substructure, the ice road has to be a certain thickness to accommodate the two million pound vehicle. Further complications arise when bridges must be built to traverse a river or other wet area. Although typically temporary, a bridge fashioned of solid ice and capable of supporting a two-million pound vehicle is a complex and expensive proposition.
Accordingly, there is a need in the art for an improved method and apparatus for transporting an oil rig.